Smythe was an English officer, and had a daughter in England. He was one of the commanding officers of Lanark. In 1296, while sitting down, he noticed a townsperson named Murron MacClannough, and began stalking her. He followed her and asked if he could help her, and when she refused, he began making a pass at her and saying how she reminded him of his daughter. He took the basket and threw it on the ground, and tried to rape her inside a hut, but her secret husband William Wallace decked him into a wall, knocking him out. He tried to help her escape, but Smythe cried out "you bastard!" to Wallace, so the soldiers tried to pursue him. Instead, they caught Murron and the magistrate, Charles Heselrig, slit her throat. Even Smythe showed remorse, looking saddened by her death. When Heselrig lured Wallace back into town, Wallace killed several soldiers. Smythe tried to slash Wallace from behind, but his friend Hamish Campbell buried an axe into his back.